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S4 W2 Cardiac Tamponade > Tamponade Pathophysiology > Flashcards

Tamponade Pathophysiology Flashcards

1
Q

What is Cardiac Tamponade?

A

Compression of the heart by fluid within the pericardiac which impairs diastolic filling of both ventricles

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2
Q

Pathophysiology of Tamponade?

A
  1. Fluid, blood, clots, pus, gas or combinations accumulate in pericardial sac
  2. Increased intra-pericarddal pressure(IPP)
  3. Compression
  4. Impeded diastolic filing of both ventricles
  5. Systemic and pulmonary congestion
  6. Decreased SV and CO
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3
Q

Clinical signs of tamponade: signs of systemic and pulmonary congestion?

A
  • JVD (jugular vein distention)
  • Hepatomegaly
  • Ascites
  • Peripheral oedema
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4
Q

Clinical signs of tamponade: signs of reduced SV and CO?

A
  • Hypotension/shock
  • Reflex tachycardia
  • Pulsus paradoxus
  • Most overt clinical signs of tamponade relate to reduced SV and CO
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5
Q

What are the most common clinical findings in tamponade?

A
  1. Tachycardia
  2. Elevated jugular venous pressure
  3. Pulsus paradoxus
    (Note: up to 30% of tamponade pts will not have classic clinical features)
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6
Q

Is tamponade an echo or clinical diagnosis?

A
  • Clinical diagnosis
  • Echo can be useful in confirming diagnosis when classic clinical signs are absent
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7
Q

What are transmural filling pressures (TMFP)?

A
  • Describes the difference in pressure between the inside and the outside of the heart
  • TMFP = ICP - IPP
  • TMFP is positive: prevents cardiac chambers from collapsing, even when pressure inside the heart is zero
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8
Q

Normal thoracic cavity pressure (ITP) and pericardial cavity pressure (IPP)?

A
  • Normally ITP is almost the same as pressure in the pericardium (IPP)
  • Both of these pressure are usually sub atmospheric or slightly negative
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9
Q

Normal heart pressure (ICP)?

A
  • ICP is normally positive, buy may be zero at end-diastole
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10
Q

What pressure is pulmonary venous return influenced by?

A

Pulmonary veins contained entirely within thoracic cavity so influenced by ITP

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11
Q

What pressure is systemic venous return influenced by?

A
  • IVC and SVC are not entirely contained within the thoracic cavity
  • IVC in abdominal cavity so influenced by intra-abdominal pressure (IAP) as well as ITP
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12
Q

Normal right heart filling with inspiration?

A
  • Diaphragm descends resulting in increased IAP (intra-abdominal pressure) and reduced ITP
  • Augments systemic venous return
  • Increased right heart filling
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13
Q

Normal right heart filling with expiration?

A
  • Diaphragm moves up
  • Decreased IAP
  • Increased ITP
  • Decreases systemic venous return
  • Reduced right heart filling
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14
Q

Normal left heart filling with respiration?

A
  • Minimal variation as pulmonary veins contained within thoracic cavity
  • Changes in ITP transmitted to pericardial sac and pulmonary veins
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15
Q

Normal left heart filling with inspiration?

A
  • As ITP falls with inspiration, so too does pulmonary venous pressure and IPP
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16
Q

Normal left heart filling with expiration?

A
  • ITP, pulmonary venous pressure and IPP all increase to the same degree
17
Q

Normal arterial pressure over respiration?

A
  • Increased RV filling during inspiration causes IVS to bow slightly towards the left
  • Slight respiratory reduction in LV filling and LV SV
  • Also slight inspiratory fall in systemic arterial systolic pressure (< 10mmHg)
18
Q

What is ventricular interdependence?

A
  • Changes to the size, shape, pressure and volume of one ventricle affects the size, shape, pressure and volume of the other ventricle
  • Normal ventricular interaction is minimal
19
Q

Normal ventricular interdependence?

A
  • With inspiration;
    1) increased RV filling slightly
    2) reduces LV filling which leads to
    3) slight decrease in CO and slight
    4) decrease in systemic arterial pressure
20
Q

Changes in transmural filling pressure with tamponade?

A

Decreased

21
Q

Changes in right and left heart filling with respiration in tamponade?

A

Exaggerated primarily due to increased IPP

22
Q

Changes in ventricular interdependence with tamponade?

A

Enhanced

23
Q

Transmural Filling Pressures (TMFP) with tamponade?

A
  • As IPP rises, ICP also rises in an attempt to maintain positive TMFP and adequate CO
  • As IPP becomes more positive despite increase in ICP, resultant TMFP becomes negative, resulting in collapse of cardiac chambers
24
Q

Left heart filling with tamponade?

A
  • ITP falls with inspiration as normal, ITP fall transmitted to pul. veins as normal
  • However, IPP elevated so diastolic filling gradient between pul. veins and left heart falls during inspration
  • With inspiration, left heart filling is decreased more than normal
25
Q

Right heart filling with tamponade?

A
  • Reduced left heart filling during inspiration results in leftward shift of IVS which enhances right heart filling with inspiration
26
Q

How does right and left heart filling in tamponade contribute to pulsus paradoxus?

A

Reduced LV volume with inspiration results in decreased LV SV leading to pulsus paradoxus

27
Q

What is pulsus paradoxus?

A
  • Exaggeration of the normal inspiratory variation os systolic pressure
  • Defined by > 10mmHg drop in systolic arterial pressure with inspiration
28
Q

What is Beck’s Triad?

A
  • 3 clinical signs associated with tamponade:
    1. Increased venous pressure (as evident by JVD)
    2. Decreased arterial pressure
    3. Muffled heart sounds
29
Q

Exaggerated ventricular interdependence with tamponade?

A
  • Increased right heart filling with inspiration = IVS shifts left and impedes LV filling
  • Increased left heart filling with expiration = IVS shifts right and impedes impedes RV filling
  • Exaggerated IVS motion due to increased IPP = limits normal expansion of ventricles
  • Ventricles competing for limited space in pericardial sac
30
Q

Effect of slow effusion (slow rate of fluid accumulation)?

A
  • Pericardium has time to stretch
  • Increased compliance
  • Larger volume can accumulate before critical election in IPP is reached
  • Once stretch limit reached, any additional increase in fluid = large increase in IPP = critical tamponade
31
Q

Effect of rapid effusion (rapid rate of fluid accumulation)?

A
  • Seen with spontaneous or iatrogenic cardiovascular perforations
  • Pericardium non-compliant
  • Small volume of fluid = marked elevation in IPP
  • Limit of pericardial stretch reached earlier
  • Critical tamponade reached earlier at smaller pericardial volumes
32
Q

Does the volume of pericardial fluid cause tamponade?

A
  • It’s not the fluid but pressure within pericardial space (and degree of pericardial constraint) that causes tamponade
  • Can have large effusion without tamponade physiology

S4 W2 Cardiac Tamponade (2 decks)

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